Bolt assembly for semi-automatic firearms



Oct. 17, 1967 LOFFLER ET AL BOLT ASSEMBLY FOR SEMI-AUTOMATIC FIREARMS 2 Sheets-Sheet 1 Filed Oct. 26, 1965 Oct. 17, 1967 O F R ET AL 3,346,982

BOLT ASSEMBLY FOR SEMI-AUTOMATIC FIREARMS Filed Oct. 26, 1965 2 Sheets5heet 2 U ite S t s P m 3,346,982 BOLT ASSEMBLY FOR, SEMI-AUTOMATIC FIREARMS Theodor Liifller, Mullheim, Baden, and Gerhard Frendlg, Hugelheim uber Mullheim, Baden, Germany, asslgnors to Rheinmetall G.m.b.H., Dusseldorf, Germany, a German company Filed Oct. 26, 1965, Ser. No. 505,263 Claims priority, application Germany, Oct. 29, 1964, R 39,130 3 Claims. (Cl. 42-16) ABSTRACT OF THE DISCLOSURE In an automatic firearm having a straight-pull bolt, the bolt is guided into position for locking by the cooperation of a plurality of pairs of guide lugs at one location along the bolt and a plurality of guide tracks extending longitudinally of the firearm receiver for substantially the entire length of the path traversed by the lugs, with clearances being provided between the lugs and tracks and between the other end of the bolt and a bolt holder to accommodate manufacturing tolerances.

This invention relates to automatic firearms and, more particularly, to such firearms having a straight-pull or axial movement bolt mechanism which is rigidly or semirigidly locked to a receiver, comprising a bolt head slidably guided in a weapon casing or receiver and which can be locked to the weapon casing by means of a control piece acting on locking bodies, such as rollers, cylinders or lugs. Bolts or breech mechanisms of this general type are known.

It is an object of this invention to provide a firearm of the above-mentioned type in which the bolt, upon engaging a cartridge base, can locate itself in, or oscillate into, a position which is within the manufacturing tolerances which are provided in the weapon in question, so that no forcing and resultant distortion of the bolt and of the adjacent parts of the casing will occur. At the same time, the operating faults and weapon firing inaccuracies due to such distortion are avoided.

According to the present invention, this object is achieved by a unique arrangement and design of the guide elements for the bolt, in that the bolt is provided with guide lugs at its front portion which are guided with a clearance along guide tracks formed in the weapon casing, and is mounted with a clearance in a receiving bore of a bolt holder at its rear terminal portion, which is preferably of cylindrical form.

As a result of the provision of these guide means and the given clearances within the same, the bolt, as stated above, can oscillate into a locked position in which, owing to the elimination of forcing, the weapon casing is also protected from abnormal stresses and deformation. This feature not only has the effect of increasing the life of the components of the weapon, but, inter alia, also has an advantageous elfect on the accuracy of the weapon.

In accordance with a subsidiary feature of the invention, the guide lugs are made very narrow in relation to the overall length of the bolt head, so that their effective guiding length is relatively small.

In a preferred embodiment of the bolt or breech mechanism according to the invention, the above-mentioned guide lugs are arranged in pairs and so designed that each 3,346,982 Patented Oct. 17, 1967 pair of lugs encloses slide surfaces diverging with increasing distance from the guide lugs.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds when taken in connection with the accompanying drawings, in which- FIGURE 1 is a side elevation partly in section of a straight-pull bolt or breech mechanism embodying the invention, and adjacent parts, the bolt being in the forward or closed position;

FIGURE 2 is a plan view of the mechanism of FIG- URE 1 also partly in section; and

FIGURE 3 is a section on the line A-B in FIGURE 1.

Referring now more particularly to the drawing, the present invention is there shown as embodied in an assault rifle having a barrel 1 with a chamber 2, a weapon casing 3 or receiver, and a bolt holder 4 for receiving a. bolt mechanism and which is movable in response to propellant gas forces upon firing of the weapon. The bolt has a head 5 which is provided, adjacent its forward end, with guide lugs 6, 6 and 7, 7 (FIGURE 3), which are arranged in pairs and guided, with perceptible bearing clearance, along guide tracks 8, 9 formed in the weapon casing. The rear, cylindrical end 10 of the bolt head 5 is mounted in a receiving bore 11 of the bolt holder 4, with a clearance space as indicated at 12a. In one weapon constructed in accordance with this invention, specifically in a gas-operated rifle variation of an assault rifle now in use by armies of West Germany and other Northern Atlantic Treaty Organization nations this clearance in the receiving bore is about 0.3 to 0.4 mm.

The bolt head 5 is able, due to the effect of the guide means and the clearances provided, to freely locate itself in, and oscillate into, the locking position (i.e. within the limits of the manufacturing tolerances which are provided), in which locking rollers 12, 12 on the bolt head engage abutments 16, 16' in a locking piece 13, so that in the final result the problems referred to above are solved with a structurally simple means and in a neat manner from the point of view of design.

In a gas-operated rifle, the above-described bolt assembly operates substantially in the following manner:

As soon as the gas pressure derived from a tapping hole or port in the barrel of the weapon acts on the gas piston (not shown) arranged in the forward extension of the bolt holder 4, the latter is moved rearwardly, in the direction of the arrow a. During this movement, a driving peg 14 mounted on the bolt holder 4 carries a bolt piece 15 along in the same direction to a certain extent, namely until the locking rollers 12, 12' come out of engagement with the abutments 16, 16' in the locking piece 13 which is fixed to the weapon casing 3. As soon as the rollers 12, 12 are out of engagement, the bolt head 5 is unlocked, and is then pulled along in the direction of the arrow a by the driving peg 14 acting on rear edge 17 until the bolt has reached its point of reversal, so that on the next forward movement the bolt is able to feed a fresh cartridge. As soon as the latter has been introduced into the chamber 2, firing is effected in known manner by Way of a firing pin 18, for example by means of a conventional hammer controlled by a trigger.

In the drawing and specification there has been set forth a preferred embodiment of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.

What is claimed is:

1. In an automatic firearm having a receiver, a straightpull bolt including a locking end adapted to be locked with the receiver on longitudinal movement relative thereto, a control piece and locking bodies operatively connected to said bolt and said control piece for locking said bolt with said receiver upon actuation thereof by said control piece, the combination therewith of means for supporting the bolt for movement into locked position comprising:

a plurality of pairs of guide lugs fixed on said bolt adjacent the locking end thereof and having a longitudinal dimension which is small in relation to the longitudinal dimension of said bolt,

a plurality of guide tracks within the receiver and extending longitudinally thereof for the entire distance traversed by said guide lugs during movement of said bolt into the locked position,

each pair of guide lugs being spaced a small distance from a corresponding one of said guide tracks and engaging said one guide track so as to be restrained substantially to longitudinal movement only along said one guide track and thus preclude turning movement of said bolt about the longitudinal axis thereof while permitting limited misalignment thereof relative to said receiver, and

a bolt holder movable longitudinally of the receiver upon firing of the firearm and having a bore therethrough encircling the other end of the bolt with a clearance space being provided therebetween,

said small distances and clearance space between said guide lugs and guide tracks and between said bolt and said bolt holder permitting accommodation of manufacturing tolerances present in the firearm.

2. A firearm as claimed in claim 1 wherein the engaging surfaces of said guide tracks and lugs diverge outwardly of the bolt.

3. A firearm as claimed in claim 1 wherein said other end of the bolt is the rearward end and is of cylindrical form.

References Cited UNITED STATES PATENTS 1,161,172 11/1915 Frommer 4216 1,344,911 6/ 1920 Lewis 89188 X 2,468,784 5/1949 Seagraves 89191 X 2,648,153 8/1953 Dicke 42-16 2,921,502 1/1960 Amsler 89188 X FOREIGN PATENTS 654,547 6/1951 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner.

S. C. BENTLEY, Assistant Examiner. 

1. IN AN AUTOMATIC FIREARM HAVING A RECEIVER, A STRAIGHTPULL BOLT INCLUDING A LOCKING END ADAPTED TO BE LOCKED WITH THE RECEIVER ON LONGITUDINAL MOVEMENT RELATIVE THERETO A CONTROL PIECE AND LOCKING BODIES OPERATIVELY CONNECTED TO SAID BOLT AND SAID CONTROL PIECE FOR LOCKING SAID BOLT WITH SAID RECEIVER UPON ACTUATION THEREOF BY SAID CONTROL PIECE, THE COMBINATION THEREWITH OF MEANS FOR SUPPORTING THE BOLT FOR MOVEMENT INTO LOCKED POSITION COMPRISING: A PLURALITY OF PAIRS OF GUIDE LUGS FIXED ON SAID BOLT ADJACENT THE LOCKING END THEREOF AND HAVING A LONGITUDINAL DIMENSION WHICH IS SMALL IN RELATION TO THE LONGITUDINAL DIMENSION OF SAID BOLT, A PLURLAITY OF GUIDE TRACKS WITHIN THE RECEIVER AND EXTENDING LONGITUDINALLY THEREOF FOR THE ENTIRE DISTANCE TRAVERSED BY SAID GUIDE LUGS DURING MOVEMENT OF SAID BOLT INTO THE LOCKED POSITION, EACH PAIR OF GUIDE LUGS BEING SPACED A SMALL DISTANCE FROM A CORRESPONDING ONE OF SAID GUIDE TRACKS AND ENGAGING SAID ONE GUIDE TRACK SO AS TO BE RESTRAINED SUBSTANTIALLY TO LONGITUDINAL MOVEMENT ONLY ALONG SAID ONE GUIDE TRACK AND THUS PRECLUDE TURNING MOVEMENT OF SAID BOLT ABOUT THE LONGITUDINAL AXIS THEREOF WHILE PERMITTING LIMITED MISALIGNMENT THEREOF RELATIVE TO SAID RECEIVER, AND A BOLT HOLDER MOVABLE LONGITUDINALLY OF THE RECEIVER UPON FIRING OF THE FIREARM AND HVING A BORE THERETHROUGH ENCIRCLING THE OTHER END OF THE BOLT WITH A CLEARANCE SPACE BEING PROVIDED THEREBETWEEN, SAID SMALL DISTANCES AND CLEARANCE SPACE BETWEEN SAID GUIDE LUGS AND GUIDE TRACKS AND BETWEEN SAID BOLT AND SAID BOLT HOLDER PERMITTING ACCOMMODATION OF MANUFACTURING TOLERANCES PRESENT IN THE FIREARM. 